Semiconductor device and method for manufacturing the semiconductor device

ABSTRACT

At least a part of a heat radiation member ( 9 ) connected to a DRAM ( 11 ) for radiating heat of the DRAM ( 11 ) is exposed from a protection member ( 4 ) arranged to surround the DRAM and the heat radiation member ( 9 ) so as to protect the DRAM ( 11 ). Thus, it is possible to provide a semiconductor device having a preferable heat radiation performance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase application of InternationalApplication No. PCT/JP2008/053768, filed Mar. 3, 2008, and claims thepriority of Japanese Application Nos. 2007-055351, filed Mar. 6, 2007,and 2007-091083, filed Mar. 30, 2007, the contents of all of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a semiconductor device and a method formanufacturing the semiconductor device.

BACKGROUND ART

Conventionally, a semiconductor device comprising a substrate on which acircuit pattern is formed and a protection member, disposed to surroundthe substrate, for protecting the substrate is known. In such asemiconductor device, a heat radiating member for radiating heatgenerated in the substrate is adhered to the surface of the protectionmember through an adhesive layer.

DISCLOSURE OF THE INVENTION

Heat of the substrate is transferred to the heat radiating memberthrough the protection member and the adhesive layer because theprotection layer and the adhesive layer are interposed between thesubstrate and the heat radiating member. The protection layer and theadhesive layer are the thermal resistance, which deteriorates the heatradiation performance from the substrate.

In view of the foregoing, one object of the present invention is toprovide a semiconductor device with high heat radiation performance anda method for manufacturing the semiconductor device.

In accordance with one aspect of the present invention, a substrate, aheat radiating member joined to the substrate and radiating heat of thesubstrate, and a protection member surrounding the substrate and theheat radiating member for protecting the substrate are provided. Atleast a part of the heat radiating member is exposed from the protectionmember.

In accordance with another aspect of the present invention,superimposing a substrate through which one or more penetrating membersused for heat transfer are provided and a heat radiating member forradiating heat of the substrate on each other, coupling the penetratingmembers to the heat radiating member while keeping the substrate and theheat radiating member superimposed on each other, having the substrateand the heat radiating member joined to each other through thepenetrating members, surrounded with a protection member, and exposingat least a part of the heat radiating member from the protection memberby removing a part of the protection member are included.

According to the present invention, heat generated in the substrate istransferred to the heat radiating member without passing through aprotection member or an adhesive layer and then radiated by the heatradiating member. Therefore, heat generated in the substrate can beefficiently radiated without upsizing the semiconductor device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically showing a semiconductor device accordingto a first embodiment of the present invention;

FIG. 2 is a view showing a method for manufacturing a semiconductordevice shown in FIG. 1;

FIG. 3 is a view showing a method for manufacturing a semiconductordevice shown in FIG. 1;

FIG. 4 is a view schematically showing a semiconductor device accordingto a second embodiment of the present invention;

FIG. 5 is a view schematically showing a semiconductor device accordingto a third embodiment of the present invention;

FIG. 6 is a view showing a comparison example with respect to asemiconductor device according to the present invention;

FIG. 7 is a graph showing a simulation result of a relationship betweena wind velocity and a highest temperature in a package when cooling windis blown to the surface of a heat radiating member of the semiconductordevice shown in FIG. 1; and

FIG. 8 is a graph showing a simulation result of a relationship betweena heat radiation area of the surface of a heat radiating member providedin a DRAM shown in FIG. 1 and a highest temperature in a package.

EXPLANATIONS OF LETTERS OR NUMERALS

-   1 semiconductor chip-   1 a surface of semiconductor chip-   1 b back of semiconductor chip-   11 substrate (DRAM)-   2 penetrating member for heat transfer (thermal via)-   3 resin adhesive (underfill)-   4 protection member (overmold)-   5 interposer-   7 adhesive layer-   8 heat radiating member-   9 dummy layer-   9 a surface of heat radiating member-   10 semiconductor device-   11 DRAM-   12 plate member-   13 hole-   14 thermal conductor-   15 semiconductor device-   16 projections and depressions

BEST MODE FOR CARRYING OUT THE INVENTION

Exemplary embodiments of the present invention will be described belowwith reference to the drawings. In the following discussion, theexemplary embodiments in which the present invention is applied to asemiconductor device 10 having a three-dimensional structure are shown.

The semiconductor device 10 according to this embodiment comprises aDRAM 11 as shown in FIG. 1.

In the example shown in the figure, the DRAM 11 has eight sheets ofsemiconductor chips 1 each on which a DRAM circuit pattern is formed.Each semiconductor chip 1 is formed by separating a wafer (not shown inthe figure) of, for example silicon, into a plurality of regions each onwhich a circuit pattern is formed. The semiconductor chips 1 are stackedwith spacings therebetween. Furthermore, the semiconductor chips 1 areconnected by metal wiring (not shown in the figure) for electricallyconnecting between the semiconductor chips 1. A plurality of thermalvias 2 used for heat transfer are provided in each semiconductor chip 1in such a manner as to penetrate the semiconductor chip. Each thermalvia 2 is formed from a material having a high thermal conductivity suchas copper or poly-silicon. In the case where each thermal via 2 isformed from copper, the thermal conductivity is 392 W/m° C. In the casewhere each thermal via 2 is formed from poly-silicon, the thermalconductivity is 148 W/m° C.

The semiconductor device 10 comprises an underfill 3 disposed tosurround the DRAM. The underfill 3 is formed from epoxy resin havingadhesion such as, for example, aliphatic epoxy resin or ether epoxyresin. The underfill 3 acts to reinforce the semiconductor device 10 byfilling the spacings between the semiconductor chips 1 and protect theDRAM 11. The thermal conductivity of the underfill 3 is 0.7 W/m° C. inthe example of the figure. The semiconductor device 10 further comprisesan overmold 4 that is a protection member for protecting eachsemiconductor chip 1. The overmoled 4 is formed from, for example epoxyresin and ceramic, and is disposed to surround the outside of theunderfill 3. The thermal conductivity of the overmold 4 is 0.7 W/m° C.in the example of the figure.

Above a top-layer semiconductor chip 1 of the stacked eight sheets ofthe semiconductor chips 1 that structure the DRAM 11, a heat radiatingmember 9 is disposed. In the example of the figure, the heat radiatingmember 9 is a plate member formed from, for example metal and ceramic,and is disposed substantially parallel to the top-layer semiconductorchip 1. The heat radiating member 9 is coupled to each thermal via 2.Thus, the heat radiating member 9 is joined to the DRAM 11 through eachthermal via 2.

In the example of the figure, the heat radiating member surface side ofthe underfill 3 and the overmold 4 is removed so that the surface of theheat radiating member 9 is exposed from the underfill 3 and the overmold4 to the external of the semiconductor device 10. Concavo-convexportions are provided on the surface 9 a of the heat radiating member 9,which enables the area in which the heat radiating member 9 contacts theatmosphere to be larger, and hence the heat radiation area to be larger.

Heat generated from each semiconductor chip 1 is transferred to the heatradiating member 9 through each thermal via 2 and then radiated to theatmosphere from the surface 9 a of the heat radiating member 9. In thecase where a logic LSI such as a CPU or a GPU (not shown in the figure)is connected to the DRAM 11, a part of heat generated from the logic LSIis transferred to the heat radiating member 9 through each thermal via 2and then radiated to the atmosphere from the surface 9 a of the heatradiating member 9. In order to improve the heat radiation efficiency, afluid that is a heat medium may be flowed on the surface 9 a of the heatradiating member 9 so that the fluid carries the heat away.

A method for manufacturing the semiconductor device 10 shown in FIG. 1will be described referring to FIGS. 2 and 3,

In order to manufacture the semiconductor device 10, a hole 13 for thethermal via 2 is formed by etching at each of a plurality of positionson a surface 1 a of one of two semiconductor chips 1 and at each of aplurality of corresponding positions on a surface 1 a of the other ofthe two semiconductor chips 1. As shown in FIG. 2( a), the twosemiconductor chips 1 are positioned in such a manner that the holes 13of the one of the semiconductor chips 1 faces the corresponding holes 13of the other of the semiconductor chips 1. Each hole 13 is filled with athermal conductor 14 such as copper or poly-silicon. Next, as shown inFIG. 2( b), the thermal conductor 14 filled in each hole 13 of the oneof the semiconductor chips 1 is coupled to the thermal conductor 14filled in the corresponding hole 13 of the other of the semiconductorchips 1 by applying plating. Thus, the both semiconductor chips 1 arejoined to each other. As shown in FIG. 2( c), the back 1 b of eachsemiconductor chip 1 is grinded to reduce the thickness of thesemiconductor chip 1 so that the thermal conductor 14 filled in eachhole 13 is exposed. Thus, a plurality of thermal vias 2 penetrating thestacked two semiconductor chips 1 are formed while a two-layeredstructure is formed. Then, as shown in FIG. 2( d), a surface 1 a of anew semiconductor chip 1 on which each hole 13 is formed is positionedto face the back 1 b of one of the above two semiconductor chips 1.Thus, a three-layered structure in which a plurality of thermal vias 2are formed is formed by similar means as described above. A similaroperation is repeated to form the DRAM 11 by stacking the eight sheetsof semiconductor chips 1.

In the example of the figure, the DRAM 11 and the heat radiating member9 are joined to each other after the DRAM 11 is formed. Here, each hole13 is previously formed at a position corresponding to each thermal via2 on the back 9 b of the heat radiating member 9 (see FIG. 2( e)). Theheat radiating member 9 is positioned in such a manner that the back ofthe heat radiating member 9 faces the top-layer semiconductor chip 1 ofthe DRAM 11. Next, each hole 13 of the heat radiating member 9 is filedwith a thermal conductor 14. The thermal conductor 14 filled in eachhole 13 on the heat radiating member 9 is coupled to the correspondingthermal via 2 by plating. Thus, as shown in FIG. 2( e), the DRAM 11 towhich the heat radiating member 9 is joined through each thermal via 2is completed. The heat radiating member 9 according to the presentinvention structures a dummy layer continuously stacked on the pluralityof semiconductor chips 1 forming the DRAM 11. In the case where aconductive metal that can be plated is used as the heat radiating member9, it is not required to provide the holes 13 in the dummy layer 9. Insuch a case, the heat radiating member 9 can be directly joined to thetop-layer semiconductor chip 1 by, for example, adhesive material.

Thereafter, the layered structure having the DRAM 11 and the heatradiating member 9 stacked on the DRAM 11 is housed in a mold (not shownin the figure). The underfill 3 of liquid adhesive resin is poured intothe mold to fill spaces between the semiconductor chips 1 and a spacebetween the DRAM 11 and the heat radiating member 9 while having thelayered structure surrounded with the underfill 3. Then, the underfill 3is hardened to complete the layered structure surrounded with theunderfill 3 as shown in FIG. 3( a). Furthermore, this structure ishoused in a moled (not shown in the figure). The overmold 4 of liquidresin is poured into the mold to have this structure surrounded with theovermold 4. Then, the overmold 4 is hardened to complete the structurewith the underfill 3 surrounded with the overmold 4 as shown in FIG. 3(b).

Finally, the overmold 4 and the underfill 3 in the upper portion of thisstructure are removed by grinding to expose the surface 9 a of the heatradiating member 9 from the overmold 4 and the underfill 3. Furthermore,the underfill 3 within the concave portions on the surface 9 a of theheat radiating member 9 is dissolved by solvent to complete thesemiconductor device 10 as shown in FIG. 3( c).

According to this embodiment, the heat radiating member 9 is joined tothe top-layer semiconductor chip 1 of the plurality of semiconductorchips 1 forming the DRAM 11, and the surface of the heat radiatingmember 9 is exposed from the underfill 3 and the overmold 4 as describedabove.

For example, as shown in a semiconductor device 15 in FIG. 6, in thecase where the DRAM 11 having a plurality of semiconductor chips 1 issurrounded with the overmold 4 and a heat radiating plate 8 is adheredto the surface of the overmold 4 through an adhesive layer 7, heat ofthe DRAM 11 is transferred to the heat radiating plate 8 through theovermold 4 and the adhesive layer 7, which deteriorates the heatradiation efficiency. The heat radiation performance is improved to someextent if the size of the heat radiating plate 8 is increased, but whichmay bring the aim of downsizing the semiconductor device by stacking thesemiconductor chips 1 to naught. Furthermore, although the heatradiation performance is improved by increasing a wind velocity ofcooling air, there are problems that power consumption of a ventilatingfan is increased and the noise is increased. In the example shown inFIG. 6, a logic LSI 6 is disposed below the DRAM 11. The logic LSI 6 isconnected to the DRAM through an interposer 5. The interposer 5 is forproviding a wiring interface between the DRAM and the logic LSI 6.

In contrast, according to the embodiment of the present invention, heatgenerated in each semiconductor chip 1 can be transferred to the heatradiating member 9 without passing through the overmold 4 or adhesivelayer 7 as shown in FIG. 6 and then radiated from the heat radiatingmember 9. Thus, heat generated in the DRAM 11 can be efficientlyradiated without upsizing the semiconductor device 10.

According to the embodiment of the present invention, a plurality ofthermal vias 2 having a significantly higher thermal conductivity thanthose of the underfill 3 and the overmold 4 are provided in eachsemiconductor chip 1, and the heat radiating member 9 is coupled to eachthermal via 2, as described above. Therefore, heat generated in eachsemiconductor chip 1 can be more surely transferred to the heatradiating member 9.

Furthermore, according to the embodiment of the present invention, inthe stacking process for the plurality of semiconductor chips 1, theheat radiating member 9 is joined to the top-layer semiconductor chip 1in a similar way to the stacking method for each semiconductor chip 1.Therefore, the heat radiating member 9 can be more easily assembled tothe DRAM 11 as compared to the case where the heat radiating member 9 isjoined to the DRAM 11 after the underfill 3 and the overmold 4 areformed in the surrounding of the DRAM 11.

In the case where the heat radiating member 9 and each thermal. via 2are formed from metal, it is required to apply heat to the heatradiating member 9 and each thermal via 2 when they are joined. In theembodiment of the present invention, because the heat radiating member 9and each thermal via 2 are joined prior to forming the underfill 3 andthe overmold 4 in the surrounding of the DRAM 11, it is prevented thatthe underfill 3 and the overmold 4 formed from resin are dissolved dueto the heat for joining the heat radiating member 9 and each thermal via2.

In contrast, in the case where each thermal via 2 of the top-layersemiconductor chip 1 of the DRAM 11 is exposed after the underfill 3 andthe overmold 4 are formed in the surrounding of the DRAM 11, and thenthe heat radiating member 9 is joined to the semiconductor chip 1, theunderfill 4 and the overmold 4 formed from resin may be dissolved byheat applied for the metal joining.

In the example shown in FIGS. 1 through 3, a plurality of holes 13 areformed in the back 9 b of the heat radiating member 9 and the holes 13are filled with thermal conductors 14, which are coupled to thecorresponding thermal conductors on the top-layer semiconductor chip 1by plating. Alternatively, the thermal conductors 14 on the top-layersemiconductor chip 1 may be directly joined to the back 9 b of the heatradiating member 9 without forming the holes 13 on the back 9 b of theheat radiating member 9.

Furthermore, in the example shown in FIGS. 1 through 3, thesemiconductor chips 1 are coupled with each other when the DRAM 11 isformed. Alternatively, after a plurality of the wafers are stacked andjoined. to each other, the stacked wafers may be separated into aplurality of regions to form the DRAM 11.

In the example shown in FIGS. 1 through 3, the surface 9 a of the heatradiating member 9 is exposed from the overmold 4 and the underfill 3.In place of, or in addition to this, the side surface of the heatradiating member 9 may be exposed from the overmold 4 and the underfill3, or the entire or a part of the surface 9 a of the heat radiatingmember 9 may be exposed from the overmold 4 and the underfill 3.

FIG. 4 schematically shows a semiconductor device according to a secondembodiment of the present invention. In this semiconductor device 10,the heat radiating member 9 as shown in FIGS. 1 through 3 is notprovided. Projections and depressions 16 are provided on a surface 4 aof the overmold 4. Therefore, the surface area of the overmold 4 isincreased, from which heat of the DRAM 11 is directly radiated. Unlike aconventional case where a heat radiating member is attached to thesurface 4 a of the overmold 4, an adhesive layer is not required. Thus,the heat radiation efficiency can be surely improved as compared to thecase where heat is transferred to the heat radiating member through theadhesive layer and the overmold.

In FIG. 4, the surface area of the overmold 4 is increased by formingexcessively large projections and depressions 16. Alternatively, thesurface area of the overmold 4 may be increased by making the surface 4a of the overmold 4 uneven by applying mechanical processing such asshot blasting or applying chemical processing such as etching.

FIG. 5 schematically shows a semiconductor device 10 according to athird embodiment of the present invention. In this semiconductor device10, a plate member 12 is disposed above the surface 4 a of the overmold4 shown in FIG. 4 in such a manner as to be spaced apart from thesurface 4 a of the overmold 4 and substantially parallel to the surface4 a. If cooling fluid is flowed between the overmold 4 and the platemember 12, turbulence occurs. Therefore, the heat transfer efficiencycan be improved as compared to a liquid flow by the natural convectionand a laminar flow when fluid is flowed merely on the surface of theovermold 4.

In FIG. 5, the plate member 12 is spaced apart from and substantiallyparallel to the surface 4 a of the overmold 4. Alternatively, the platemember 12 may be spaced apart from and substantially parallel to thesurface 9 a of the heat radiating member 9 of the DRAM 11 so thatcooling fluid can be flowed between the plate member 12 and the heatradiating member 9.

In the first through third embodiments, the substrate is the DRAM 11having a plurality of semiconductor chips 1. Alternatively, thesubstrate may be the DRAM 11 having a single semiconductor chip 1.

In the first through third embodiments, the semiconductor device 10comprises the DRAM 11. In place of or in addition to this, the presentinvention can be applied to a semiconductor device comprising asubstrate such as a CPU or a GPU other than the DRAM 11. In such a case,a CPU and a GPU can be formed by stacking a plurality of semiconductorchips as the DRAM 11 according to the above embodiments.

In the first through third embodiments, the heat radiating member 9 thatis a different member from the plurality of semiconductor chips 1 isjoined to the semiconductor chips 1. Alternatively, among the stackedsemiconductor chips 1, one of the upmost and downmost layers is formedwith a semiconductor chip having a radiation function for radiating heatfrom the other semiconductor chips. The semiconductor chip having aradiation function may be used as the heat radiating member.

EXAMPLES

An example according to the present invention will be described. A graphshown in FIG. 7 is a result of simulating a relationship between a windvelocity and a highest temperature in a package of the DRAM 11 whencooling wind is blown to the surface of the heat radiating member 9 ofthe DRAM 11 shown in FIG. 1. Conditions of the simulation are that theheat radiation area of the surface 9 a of the heat radiating member 9 is0.000144 m², and the cooling wind is blown along the surface 9 a of theheat radiating member 9. It should be noted that, when the wind velocityis 0.022 m/sec, the volume of the wind is at a level corresponding tothe natural convection without a cooling fan. The wind blows equally inall directions.

A graph shown in FIG. 8 is a result of simulating a relationship betweena heat radiation area of the surface 9 a of the heat radiating member 9provided in the DRAM 11 shown in FIG. 1 and the highest temperature inthe package of the DRAM 11. Conditions of the simulation are that windgenerated by the natural convection (wind velocity is 0.022 m/sec) isblown to the surface 9 a of the heat radiating member 9 without blowingcooling wind from the external to the surface 9 a of the heat radiatingmember 9 and that the wind blows equally in all directions.

As seen from FIGS. 7 and 8, when the heat radiation area of the surface9 a of the heat radiating member 9 is 0.000144 m², the highesttemperature in the package does not decrease below 100° C. unless windhaving a velocity of about 0.5 m/sec or more is blown to the surface 9 aof the heat radiating member 9. However, when the heat radiation area ofthe surface 9 a of the heat radiating member 9 is 0.00065 m² or more ,the highest temperature in the package can be decreased below 100° C.only by wind generated by the natural convection, without blowing windfrom the external to the surface 9 a of the heat radiating member 9.

The invention claimed is:
 1. A semiconductor device comprising: asubstrate; a penetrating member penetrating the substrate; a heatradiating member joined to the penetrating member for radiating heat ofthe substrate; and a protection member surrounding the substrate and theheat radiating member for protecting the substrate, wherein at least apart of the heat radiating member is exposed from the protection member.2. The semiconductor device according to claim 1, wherein the substrateincludes stacked semiconductor chips and the penetrating memberpenetrates the semiconductor chips.
 3. The semiconductor deviceaccording to claim 1, wherein a thermal conductivity of the penetratingmember is higher than a thermal conductivity of the protection member.4. The semiconductor device according to claim 1, further comprising aplate member disposed above the heat radiating member to form a spacebetween the plate member and the heat radiating member, the plate memberbeing substantially parallel to the heat radiating member.
 5. Thesemiconductor device according to claim 2, wherein the semiconductorchips are separated by at least a gap, the semiconductor device furthercomprising a resin adhesive surrounding the substrate and filling thegap, wherein at least a part of the heat radiating member is exposedfrom the resin adhesive.
 6. A semiconductor device comprising: asubstrate; a penetrating member penetrating through the substrate; and aprotection member surrounding the substrate, a surface of the protectionmember comprising projections and depressions, wherein a portion of theprotection member is in contact with the penetrating member.
 7. Thesemiconductor device according to claim 6, wherein a plate member isdisposed above the projections and depressions to form a space betweenthe plate member and the surface of the protection member, the platemember being substantially parallel to the surface of the protectionmember.
 8. The semiconductor device according to any one of claims 1, 2,3, and 4-7, wherein the substrate is a DRAM.
 9. A method formanufacturing a semiconductor device, comprising: providing a firstthermal conductor in a first substrate; superposing the first substrateand a heat radiating member for radiating heat of the substrate;coupling the first thermal conductor to the heat radiating member;surrounding the first substrate and the heat radiating member with aprotection member; and exposing at least a part of the heat radiatingmember from the protection member by removing a part of the protectionmember.
 10. The method according to claim 9, further comprising:providing a second thermal conductor in a second substrate; superposingthe first substrate over the second substrate; and coupling thesubstrates by bonding the thermal conductors provided respectively inthe substrates.
 11. The method according to claim 9, further comprising:providing a second thermal conductor in the heat radiating member; andcoupling the first substrate and the heat radiating member by bondingthe first and second thermal conductors.
 12. A semiconductor devicecomprising: a substrate including a plurality of stacked semiconductorchips; a penetrating member penetrating the plurality of stackedsemiconductor chips; a heat radiating member joined to the penetratingmember for radiating heat of the plurality of stacked semiconductorchips; and an adhesive resin filled between the plurality of stackedsemiconductor chips.
 13. The semiconductor device according to claim 12,wherein: the adhesive resin surrounds the plurality of stackedsemiconductor chips and the heat radiating member; and at least a partof the heat radiating member is exposed from the adhesive resin.